Transit at Schiphol Airport (AMS)

Visa wise, according to Timatic:

Netherlands - Transit Visa

Visa required.

The following are exempt from holding a visa:

Passengers with a Hong Kong (SAR China) passport for a maximum stay of 90 days.

Passengers with a Macao (SAR China) passport for a maximum stay of 90 days.

Transiting without a visa is possible for:

Holders of onward tickets transiting by the same or first connecting aircraft

Are you on a single ticket from HKG-LHR? If so, you'll be rebooked automatically if you miss the connection.

As for Schiphol Airport itself, since you'll be arriving from a non-Schengen country and leaving to a non-Schengen country, you'll be arriving in either Terminal 2 or 3 and leaving from one of those 2 terminals also. (these two are connected airside). These terminals are open 24h, and you should have no problem spending the night there, and if you want, you could go and sleep in one of the airside hotels.

We have done a 21 hour layover airside at Schipol, so simply staying overnight is within time limits.

We stayed at the Mercure Hotel in Terminal 3, decent room and price is on average for in terminal hotels.

1. Yes, if the plane is on time it should be enough. Otherwise the airline will take care of you because you have a single ticket

2. There is no set time limit in the Netherlands; you simply need to get the first connecting aircraft to your destination (as stated in Timatic, the database used by airlines).

3. No, you're not entering the Netherlands, and unlike in China this means no passport control.